Endless abrasive belt having an overlapping joint

ABSTRACT

An endless abrasive belt of the type including one or more sections of backing material supporting an abrasive coating and having adjacent end portions overlapped to form joints extending obliquely of a direction of belt travel is characterized by the abrasive coating on an inner one of the overlapped end portions being removed over the longitudinal extent of the overlapping and the abrasive coating on an outer one of the overlapped end portions being removed only over a longitudinal extent in a range of about 30 to 80 percent of the overlapped distance.

limited States Patent Hildebrand [54] ENDLESS ABRASIVE BELT HAVING AN OVERLAPPING JOINT [72] Inventor: Hans Hildebrand, Koeln-Nippes, Germany [73] Assignee: Norton Company, Worcester, Mass.

[22] Filed: May W, 1970 21 Appl. No.: 38,117

[30] Foreign Application Priority Data May 16, 1969 Germany ..P 19 25 1515 [52] US. Cl ..51/399 [51] [58] Field otSear-ch ..5l/399,401,407

I5 onlultsisrsnsefiited UNITED STATES PATENTS 1,009,709 11/1911 Furber ..5l/399 51 Feh.22,W72

Primary Examiner-Donald G. Kelly Attorney-Hill, Sherman, Meroni, Gross 8:. Simpson ABSTRACT An endless abrasive belt of the type including one or more sections of backing material supporting an abrasive coating and having adjacent end portions overlapped to form joints extending obliquely of a direction of belt travel is characterized by the abrasive coating on an inner one of the overlapped end portions being removed over the longitudinal extent of the overlapping and the abrasive coating on an outer one of the overlapped end portions being removed only over a longitudinal extent in a range of about 30 to 80 percent of the overlapped distance.

4 Claims, 2 Drawing Figures ENDLESS AIBRASIVE BELT HAVING AN OVERLAPPING JOINT BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to endless abrasive belts having overlapped, joints formed obliquely to a direction of travel of the belt, and more particularly refers to an abrasive belt having an abrasive coating partially removed at the overlapped ends in a region of the overlapping.

2. Description of the Prior Art Abrasion operations, employing broad, endless, abrasive belts, have been utilized during the past years not only in the woodworking arts but also in metal working industries. Oftentimes, those abrasion operations employ broad belt trains comprising several grinding or abrading stations employing belts having differently sized grain coatings. For example, an operation utilizing four stations may have two stations fitted with belts having coarse grains (grain size 40 or 50) and the two succeeding stations fitted with belts having finely sized grains (grain size 80 and finer), thereby to obtain the desired surface characteristics and finish.

Normally, the endless abrasive belt is urged against the workpiece by appropriate means, such as a contact roller or a contact pressure beam extending transversely of the belt travel over and having the abrasive belt trained thereover.

The endless abrasive belts, including a backing material supporting an abrasive, grain material, may have a width of approximately 2.6 m. a circumferential length of approximately 3.8 m. and overlapped, butt joints extending longitudinally for a distance of approximately mm. Most of the conventional abrasive belts, of which I am aware, have overlapping joints of two general types. One form of overlapped joints has the abrasive coating removed only at the lower or innermost one of the overlapped end portions along the extent of the overlapping so that the upper or outermost belt end portions is glued onto an exposed, outer surface of the backing member. With that arrangement, the coating on the outer belt end portion projects above an adjacent portion of the coating carried on the inner belt end portion. It has been found that the use of an endless abrasive belt having a joint of that configuration produces undesirable chatter marks on the workpiece. Further, with belts of that configuration, in order to prevent separation of the belt end portions at the joint, it is necessary that the belt be rotated in such a direction that the glued joint runs off the grain side, thereby preventing a terminal end of the raised, outer end portion from striking the workpiece. Rotation of the belt in that direction, however, causes a terminal end of the inner belt end portion, at the underside of the abrasive belt, to run up on the contact roller or contact pressure beam. Thus, in the event a contact pressure beam of the type which does not move with the belt travel is utilized, or if the glued joint is slightly imperfect, the constant striking of the inner belt end on the contact member may cause breakage or separation of the belt at the joint. The inherent disadvantages prove troublesome even at coarse grinding stations where the formation of chatter marks and similar flaws may be tolerated to a certain extent.

In an attempt to overcome the above-mentioned problems, some abrasive belts utilize the other type of joint which has the coating removed at both the inner end portion and the outer end portion and for an extent on each end portion which corresponds to the extent of the overlapping. With that type of joint, there is an absence of coating at the upper or outer side of the belt in the overlapped region, and a recess may be formed in the overlapped region since the grain coating removed from both of the belt end portions is oftentimes thicker than one-half of the thickness of the entire belt. That type of abrasive belt joint does not produce the undesirable chatter marks. However, when the longitudinal extent of the glued joint is approximately 10 mm. or greater, it has been found that the use of the belts having the second type of joint produce undesirable burnt spots on the workpiece. Those burnt spots appear to be attributable to heated, abraded particles being captured in the recess or gap in the coating.

Further, the removal of the coating at the outer end portion along the entire extent of the overlapped region sufficiently weakens the belt, particularly in a region of the outer end portion immediately adjacent a terminus of the inner end portion, thereby resulting in frequent breakage of the belt. It should be noted that the joint is additionally stressed in transverse directions by a reciprocating transverse movement usually superimposed at the abrasion area and over the longitudinal movement of the belt. The transverse reciprocating movement may have an extent of approximately 10 to l5 mm. and a frequency in a range of about 1 to 6 oscillations per minute.

In summary, the prior art, endless abrasive belts, of which I am aware, have the inherent disadvantages of either producing chatter marks or burnt spots on the workpiece and do not possess an adequate tearing strength.

SUMMARY OF THE INVENTION An endless abrasive belt, including one or more sections of backing material supporting an abrasive coating and having adjacent end portions overlapping to form a joint extending obliquely of a direction of belt travel, has the abrasive coating on an innermost one of the overlapped end portions removed over a longitudinal extent of the overlapping and has the abrasive coating at the outermost one of the overlapped end portions removed only over a longitudinal distance in a range of about 30 to percent of the extent of the overlapping. It has been found to be desirable to remove the abrasive coating on the outer end portion for a longitudinal distance equal to approximately 50 percent of the overlapping of the belt end portions.

In that manner, the abrasive belt has an increased thickness over a portion of the region of overlapping. However, contrary to expectations, it has been found that the abrasive belt of the present invention does not produce either chatter marks or burnt spots on the workpiece. Further, the coating on the outer end portion overlaps a terminus of the inner end portion, thereby enhancing the tearing strength of the belt in the region of the joint.

Further, it has been found that the abrasive belt of the present invention may be rotated in a direction so that the outer end portion may run up on the workpiece without any disadvantage, thereby enabling an underside of the belt or the inner end portion to run off of a contact roller or contact pressure beam urging the belt into abrading engagement with the workpiece. In that manner, breakage of the belt is lessened, since the terminus of the inner end portion will not strike the contact member. Thus, a slightly imperfect area in the glued joint will not materially influence the useful life of the abrasive belt.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an end elevational view of an endless abrasive belt constructed in accordance with the present invention; and

FIG. 2 is an enlarged, longitudinal cross-sectional view of the endless abrasive belt illustrated in FIG. l and illustrating an overlapped joint of the belt.

DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawing, an endless abrasive belt 10, constructed in accordance with the present invention, comprises one or more sections of sheet form backing material ll supporting a coating 12 composed of an abrasive grain material. The backing material 11 may be a continuous, looped band, as illustrated in FIG. 1, or, if desired, a plurality of aligned belt sections may be joined together in a manner to form a continuous loop. The endless abrasive belt 10 is trained around appropriate drive wheels in a manner to form an abrading apparatus. Contact means, such as a roller or a beam member, having the belt 10 trained thereover urges. the belt into abrading contact with a workpiece. Also, if desired, a plurality of the belts may be arranged in a side-by-side relationship and provided with abrasive coatings having difierently sized grains, thereby to progressively abrade a surface to form a desired finish.

Adjacent end portions of the sections of the backing material 11, or opposite end portions of a continuous section of the ,material, are overlapped and joined by a suitable adhesive 13 in a manner to form a joint 14 extending obliquely of a direction of belt rotation, as indicated by arrow 16 and having an outer end portion 17 overlapping an inner end portion 18.

In accordance with the principles of the present invention, the abrasive coating 16 is removed from the overlapped end portions 17 and 18 over certain regions selected to enhance a tearing strength of the joint 14 and to eliminate chatter marks and burnt spots on the finished workpiece. In particular, the abrasive coating 12 is removed from the inner end portion 18 over an area coextensive with the longitudinal extent of the overlapping between the inner end portion and the outer end portion 17, whereas the abrasive coating 12 is removed from the outer end portion over an area extending longitudinally of the backing material 11 for a distance in a range of about 30 to 80 percent of the extent of the overlapping. In that manner, the abrasive coating 12 on the inner end portion 18 terminates substantially along a juncture plane defined by a terminus 19 of the outer end portion 17, and the coating 12 on the outer end portion terminates along a plane overlying the region of .the overlapping between the end portions.

In order to further enhance the tearing strength of the joint 14, the outer overlapped end portion 17 may be outwardly offset,,as at 21, a distance substantially equal to a thickness of the backing material 11. Thus, underneath or innermost surfaces 22 of adjacent sections of the backing material 1 1 disposed on opposite sides of the joint 14 are flush or substantially coplanar.

It is contemplated by the present invention that the abrasive belt 10 be rotated in the direction indicated by. the arrow 16 so that the inner overlapped end portion 18 runs off of the contact means. In that mariner, a terminus 23 of the inner end portion 18 does not directly strike the contact means, thereby lessening wear on the joint 14 and increasing the life expectancy of the abrasive belt 10.

In a preferred example of the present invention, the extent of overlapping between the end portions 17 and 18 may be approximately 10 mm., or 0.39 inches. According to the present invention the abrasive coating 12 would be removed from the inner end portion 18 over a longitudinal extent, indicated by "a,"of approximately at 10 mm., and the coating would be removed from the outer end portions 17 over a longitudinal extent, indicated by b, of a value, within a range of about 3 v to 8 mm., and preferably 5 mm.

Although those versed in the art may suggest various minor modifications, it should be understood that I wish to encompass within the scope of the patent warranted hereon all such modifications as reasonably and properly come within the scope of my contribution to the art.

I claim as my invention:

1. In an endless, abrasive belt of the type including a stripform backing material supporting a coating of abrasive grain material, overlapped joints extending obliquely of a direction of belt travel and including an outer end portion overlapping an adjacent inner end portion, the improvement comprising:

the inner end portion having the abrasive coating removed therefrom in a region extending longitudinally inwardly of :1 terminus of the inner end'portion for a distance substantially coextensive with the extent of overlapping between the adjacent end portions; and

the outer end portion having the coating removed therefrom in a region extending longitudinally from a terminus of the outer end portion a distance in a range of about 30 to percent of the extent of overlapping.

2. In an endless abrasive belt according to claim 1, comprising the outer overlapped end portion having the abrasive coat ing removed therefrom over a region extending longitudinally inwardly of the inner end portion terminus for a distance of about 50 percent of the extent of overlapping.

3. An endless'abrasive belt according to claim I wherein the extent of overlapping between the adjacent, overlapped end portions is substantially equal to l0 mm., and wherein the outer end portion has the coating removed over a region extending longitudinally inwardly of a terminus thereof for a distance of approximately 5 mm.

4. An endless abrasive belt comprising:

means forming at least one section of sheet-form backing material arranged in a loop and having an outer end portion overlapped and adhered to adjacent inner end portion to form a joint extending obliquely of a direction of belt travel;

means forming an abrasive coating adhered to an outwardly projecting surface of said backing material, said coating on said inner end portion terminating along a juncture plane defined by a terminus of said outer end portion, and i said coating terminating on said outer end portion along a plane spaced longitudinally inwardly of said outer end portion terminus a distance in a range of 30 to 80 percent of an extent of overlapping between said adjacent end portions. 

1. In an endless, abrasive belt of the type including a stripform backing material supporting a coating of abrasive grain material, overlapped joints extending obliquely of a direction of belt travel and including an outer end portion overlapping an adjacent inner end portion, the improvement comprising: the inner end portion having the abrasive coating removed therefrom in a region extending longitudinally inwardly of a terminus of the inner end portion for a distance substantially coextensive with the extent of overlapping between the adjacent end portions; and the outer end portion having the coating removed therefrom in a region extending longitudinally from a terminus of the outer end portion a distance in a range of about 30 to 80 percent of the extent of overlapping.
 2. In an endless abrasive belt according to claim 1, comprising the outer overlapped end portion having the abrasive coating removed therefrom over a region extending longitudinally inwardly of the inner end portion terminus for a distance of about 50 percent of the extent of overlapping.
 3. An endless abrasive belt according to claim 1 wherein the extent of overlapping between the adjacent, overlapped end portions is substantially equal to 10 mm., and wherein the outer end portion has the coating removed over a region extending longitudinally inwardly of a terminus thereof for a distance of approximately 5 mm.
 4. An endless abrasive belt comprising: means forming at least one section of sheet-form backing material arranged in a loop and having an outer end portion overlapped and adhered to adjacent inner end portion to form a joint extending obliquely of a direction of belt travel; means forming an abrasive coating adhered to an outwardly projecting surface of said backing material, said coating on said inner end portion terminating along a juncture plane defined by a terminus of said outer end portion, and said coating terminating on said outer end portion along a plane spaced longitudinally inwardly of said outer end portion terminus a distance in a range of 30 to 80 percent of an extent of overlapping between said adjacent end portions. 